1. Field of the Invention
The invention relates generally to the field of microwave ovens and more specifically to a method of cooking using both microwave and infrared radiation.
2. Description of the Prior Art
In the art of cooking by use of microwaves, it is known that some foods achieve insufficient browning by the time they are fully cooked. In a conventional oven operating by means of convection or infrared heat, the outer surface is raised to an elevated temperature and heat is conducted inwards to cook the interior of the food. The outer surface cooks longer at a higher temperature than the interior, becomes drier, and therefore, becomes more browned than the interior.
In contrast, microwave radiation does not raise the surface temperature to as high a temperature for as long a time as in conventional cooking. Juices from the interior of the food rise toward the surface of the food and accumulate there in relatively greater quantities than one finds at the surface with conventional cooking. This higher moisture content has an inhibitive effect on the rate of browning. The surface, therefore, remains substantially unbrowned compared with conventionally cooked foods by the time the interior of the food is cooked.
Prior art microwave ovens have attempted to overcome the inherent inability of microwaves to brown some foods as well as conventional ovens by including in them devices to heat the food's surface by means of convection or infrared heat. With either type of device the surface temperature is raised to a higher temperature and lower water content than it would otherwise reach when under the influence of microwaves alone; and the surface "browning" is increased.
Prior art browning devices incorporated into a microwave oven, even if they have been of the infrared radiation variety, have also incorporated into them many of the conceptual limitations found in conventional ovens. Conventional ovens even today are mere mechanical improvements over stone age fired ovens. They generally operate by raising the temperature of the surroundings to a certain degree and then conducting the heat to the food by means of convection. In this regard, the burner is fired at full power until the desired temperature is achieved. Little cooking is done by infrared radiation from the burner itself. The result is a slow, energy-inefficient, hot method of cooking. By "hot" it is meant that the oven cavity and the ambient air heat up to substantial degree, a result no longer desirable in a modern kitchen.
Such a use of heating the surroundings is found in U.S. Pat. No. 3,569,656 to White et al.. In order to achieve browning, White U.S. Pat. No. 3,569,656 adopts the methods of the conventional oven. The air and surroundings are heated with Calrod resistance heaters to precisely the same temperature as one would find in a conventional oven for a similar degree of browning (bake, roast, crisp, etc.) before the microwave device is even turned on. This is nothing more than microwave assisted conventional cooking rather than browner assisted microwave cooking.
Other devices incorporated into a microwave oven with the more limited purpose of browning rather than cooking have uniformly been operated at full power for a set period of time. This is but a variation on the broil technique found in the conventional oven. The browner gets very hot and a very hard (charred) browning is achieved to a very short depth. This varies of course with the power of the browner and the distance from the food, but the use of these devices in such a manner provides for a very limited range of browning choices.
Recognizing these limitations, U.S. Pat. No. 4,137,442 to Tateda has recently provided for a variable position browner. Variations in browning are achieved by moving the browner closer to or further away from the food. However, the device is still operated at full power for a set period of time to again limit the scope of browning degrees and depths achieveable. Moreover, this browning method requires an unnecessarily complex and expensive mechanical device to achieve its purpose.
None of these devices have exhibited any attempt to coordinate the use of the browning device with that of the microwave device to optimize both browning and cooking. Further, no prior art device or method known has a range of browning choices as well as an optimized browning/cooking recipe for each type of food which may be automatically performed by a microwave oven for cooking and browning to near perfection.